LAUSR

Abstract The conformational equilibria and IR isomerisation processes of glycolaldehyde (HOCH 2 CHO) conformers have been studied at low temperature in nitrogen cryogenic matrix. The effects of selective IR irradiation, in the ν OH and ν CH domains, have been followed by FTIR spectroscopy. After deposition the main form is the most stable one, CC (Cis-Cis) , which features an intramolecular hydrogen bond. Upon selective IR irradiation, this latter form is able to interconvert into two open forms, those called TT (Trans–Trans) , and TG (Trans-Gauche) . From TT and TG forms, no recovering (by tunneling, dark process, irradiation, annealing, etc.) of the initial state (i.e. CC regeneration) has been observed. However, a TT ⇌ TG thermal equilibrium is observed with a standard reaction enthalpy about 0.37 kJ mol −1 .